Generally, a base station of a mobile communication system has been divided into a base station main unit configured to process transmit and receive signals and an antenna device including a plurality of radiating elements to transmit/receive radio signals. Usually, the base station main unit is installed at a low position on the ground, and the antenna device is installed at a high position such as a building roof or a tower, and the base station main unit and the antenna device may be connected to each other through a feeder cable or the like.
In recent years, in order to compensate for cable loss in signal transmission between the antenna and parts of the base station main unit according to enhanced ease of tower installation due to miniaturization and weight reduction of each device for radio signal processing, a structure in which a remote radio head (RRH) responsible for processing transmit and receive radio signals is installed at the front end of the antenna device is widely employed.
FIG. 1 schematically shows an example of devices installable on the side of an antenna device in a typical mobile communication base station. As shown in FIG. 1, a service band separator/combiner 16 is installed at the front end of that the antenna device. Typically, the service band separator/combiner 16 is connected to the antenna device 10 using a cable conforming to the AISG (Antenna Interface Standards Group) standard.
The service band separator/combiner 16, which is provided to additionally distinguish between service bands of the antenna device 10, serves to separate a transmitted signal from the base station main unit into signals according to respective configured service bands and provide the same to the antenna device 10 and also serves to combine signals of respective bands provided from the antenna device 10 and transmit the combined signals to the base station main unit. This service band separator/combiner 16 has a structure of a filter combiner/distributor in which a processing band is appropriately configured for the respective service bands to be separated and/or combined.
The functions of the service band separator/combiner 16 will be described in more detail. In the current mobile communication environment, not only the commercial deployment of 2G (Generation), 3G, 4G LTE (Long Term Evolution) but also the introduction of a 5G system is being considered. Various frequency bands of mobile communication services coexist according to communication systems or communication operators and countries, and the base station environment is diversified. Thereby, service bands are also frequently changed by specific operators. Accordingly, in order to realize an efficient base station system and to reduce the operating cost of the base station, the base station (and the base station antenna device) is provided with a broadband system to cover various service bands. In this environment, the service band separator/combiner 16 is additionally installed at the time of installation of the initial antenna device 10, or when necessary, so as to be able to select an appropriate service band required for a specific operator.
However, additional production and installation of the service band separator/combiner 16 has a problem of material cost and processing cost for the manufacture of a separate device, and also the installation work is difficult and costly. Particularly, in this case, the service band separator/combiner 16 is installed while being additionally connected to the antenna device 10 through a cable. Thereby, the installation is likely to raise problems regarding waterproofing of each connection part and produces a result that is not aesthetically pleasing.